Advances in integrated circuits used in high performance systems have created a demand for higher density electrical interconnections to accommodate large numbers of inputs and outputs. Methods of manufacturing high density interconnects are known to those having skill in the art, as described in U.S. Pat. No. 4,810,332 which issued Mar. 7, 1989 and in Jensen et al., "Copper/Polyimide Materials for High Performance Packaging, IEEE Transactions on Components, Hybrids, and Mfg. Tech., vol. CHMT-7 #4, pp. 383-393 (December, 1984). Fabrication of such high density interconnects will invariably include a certain percentage of defective units, for instance from shortcircuited connections or from electrical openings. These defects are usually detected during manufacturing by mechanical, optical, or voltage contrast electron beam testing. Various options are available to rework defective interconnects. A short-circuit could be severed by a laser beam or an ion beam. An open line could be closed by laser deposition, laser chemical vapor deposition, chemical vapor deposition, or ink jet metal deposition.
Copper is the preferred conductor for such high density multilayer interconnects. One drawback of copper is that it is very subject to corrosion and oxidation. To fabricate and rework reliable multilayer copper interconnects, the copper can be protected by other materials.